The first variant was designed during the 1980s, when Sukhoi was seeking to upgrade its high-performance Su-27, and was initially known as the Su-27M. Later re-designated Su-35, this derivative incorporated aerodynamic refinements to increase manoeuvrability, enhanced avionics, longer range, and more powerful engines. The first Su-35 prototype, converted from a Su-27, made its maiden flight in June 1988. More than a dozen of these were built, some of which were used by the Russian Knightsaerobatic demonstration team. The first Su-35 design was later modified into the Su-37, which possessed thrust vectoring engines and was used as a technology demonstrator. A sole Su-35UB two-seat trainer was built in the late 1990s that strongly resembled the Su-30MK family.

In 2003, Sukhoi embarked on a second modernization of the Su-27 to produce what the company calls a 4++ generation fighter that would bridge the gap between legacy fighters and the upcoming fifth generation Sukhoi PAK FA. This derivative, while omitting the canards and air brake, incorporates a reinforced airframe, improved avionics and radar, thrust-vectoring engines, and a reduced frontal radar signature. In 2008 the revamped variant, erroneously named the Su-35BM in the media, began its flight test programme that would involve four prototypes, one of which was lost in 2009.

The Russian Air Force has ordered 48 production units, designated Su-35S, of the newly revamped Su-35. Both Su-35 models marketed to many countries, including Brazil, China, India, Indonesia, and South Korea, but so far have not attracted any export orders. Sukhoi originally projected that it would export more than 160 units of the second modernized Su-35 worldwide.

In the early 1980s, while the Su-27 was entering service with the Soviet Air Forces, Sukhoi looked to develop a follow-on variant. Originally designated "Su-27M" and known internally as the "T10-M", it would be much more agile and feature greatly improved avionics compared to the aircraft considered to be the best contemporary fighter.[9] It was also to carry more armament to improve its Air-to-ground weaponry capabilities.[10]

The improved variant, the development of which began in the early 1980s,[11] featured a host of changes in aerodynamics, avionics, powerplants, and construction methods, as well as increasing payload capacity. High-strength composites and Aluminium-lithium alloys were used to reduce weight and boost internal fuel volume.[12] One of the distinguishing features of this early design were the canards, which improved airflow over the wings, eliminating buffeting and allowing the aircraft to fly at an angle of attack of 120°. These canards were governed by a new digital fly-by-wireflight-control system.[9] The aircraft was fitted with the Luylka AL-31FM(AL-35F)turbofan engine which is larger, more reliable and, with a thrust of 125 kN (28,200 lbf), more powerful than those found on the Su-27.[9]

The Su-27M (T-10S-70) prototype first flew on 28 June 1988 piloted by Sukhoi chief test pilot Oleg Tsoi.[13][17] The first prototype differed slightly from later examples in: retaining standard Su-27 vertical stabilizers without the cropped top; lacking a fire-control system; having a three-tone grey/blue camouflage scheme, along with minor differences.[13] Designated T10M-1 to T10M-10, the first ten prototypes were built by Komsomolsk-on-Amur Aircraft Production Association (KnAAPO) in conjunction with Sukhoi (as the Soviet military-industrial structure separated the aircraft designer and manufacturer).[13] They differed slightly, as four were converted from Su-27s, and the others were new-builds.[18][19] The second prototype started flying in January 1989, while the third followed in mid-1992.[13][20] The prototypes were used to validate the canards and new flight-control system.[12]

In 1990, the first prototype was displayed to Ministry of Defence officials at Kubinka Air Base.[13] The aircraft first aerial demonstration occurred on 13 February 1992, in front of CIS leaders in Machulishi, Minsk, before making its public debut at that year's Farnborough Airshow.[13][21] The third prototype, T10M-3, appeared at the Dubai Airshow in 1993, by which time Sukhoi had re-designated its fighter the "Su-35".[18][22] T10M-3 demonstrated its dogfight manoeuvres, including the Pugachev's Cobra, to potential export customers. Viktor Pugachyov subsequently piloted the prototype in a mock fight with an Su-30MK.[18] The Su-35 performed at numerous air shows during the following years, including at the 1993 and 1995 MAKS Airshows and the 1994 ILA Berlin Air Show.[18] In addition to Su-27 conversions, three production Su-35s were completed in 1996 and delivered to Russian Air Force (VVS) for testing.[23]

The sole Su-35UB (Bort 801) twin-seat trainer, which first flew in August 2000,[24] in flight alongside another Sukhoi demonstrator, the Su-47.

Throughout the Su-35's flight test programme, active controls during manoeuvres such as the Pugachev's Cobra and tailslide could not be maintained. The eleventh Su-27M (T10M-11) was built by KnAAPO and delivered in 1995 for the installation of exclusive systems to give it thrust-vectoring capabilities. The resultant Su-37technology demonstrator made its first flight in April 1996.[25][26] A second Su-35 was modified into an Su-37 in the late 1990s.[27] In 2001, AL-31F engines with fixed nozzles, an upgraded fly-by-wire controls, and improved cockpit systems were fitted to a Su-37 for testing.[24]

In total, 15 airworthy Su-35s (Su-27M) were produced, including an Su-35UB two-seat prototype, along with two static test prototypes.[2][28] The Su-35UB, powered by two modified AL-31FPs with thrust-vectoring nozzles, made its first flight on 7 August 2000. It was demonstrated to South Korea during that country's F-X replacement fighter tender, before becoming an avionics testbed.[29] The original Su-35 never entered serial production due to a lack of funding,[23] and the VVS continued to use its Su-27 fleet. The Su-35's automatic control of canards and the Su-37's thrust-vectoring technology were applied to the Sukhoi Su-30MKI.[30] One of the Su-35s, T10M-10, served as a testbed for the Saturn 117 (AL-41F1) engine intended for Russia's upcoming PAK FA fifth-generation jet fighter.[31]

In 2003, even as Russia aimed to export the Su-27M, Sukhoi launched a project to produce a fighter to bridge the gap between upgraded variants of the Su-27 and Su-30MK, and Russia's fifth-generationSukhoi PAK FA. The project's aim was a second modernization of the Su-27 airframe (hence its classification as a "4++ generation fighter") by incorporating several characteristics that would be implemented on the PAK FA.[32][33] Additionally, the aircraft was to be an alternative to the Su-30 family on the export market.[34] The design phase was to take place until 2007, when it would be available for sale.[32] It was later reported that the programme was launched due to concerns that the PAK FA project would encounter funding shortages.[35] The project's in-house designation is T-10BM (Bolshaya Modernizatsiya, "Big Modernization") while the aircraft is marketed as the Su-35.[32][36][N 2]

The Su-35 incorporated numerous differences to the Su-27M, including a shorter rearward-projecting "sting", the omission of the dorsal air brake, and the use of thrust-vectoring engines

While the aircraft maintains a strong superficial resemblance to the Su-27, the airframe, avionics, propulsion and weapons systems of the Su-35 have been thoroughly overhauled. Technological advancements have produced more compact and lighter hardware, such as the radar, shifting the centre of gravity to the aircraft's rear. These improvements removed the need for canards and saw the abandonment of the "tandem triplane" featured on several Su-27 derivatives.[32][34] Also omitted was the Su-27's dorsal airbrake, which was replaced by differential deflection of the vertical stabilizers.[37] Other aerodynamic refinements include a height reduction of the vertical stabilizers, a smaller aft-cockpit hump, and shorter rearward-projecting "sting".[32]

The reinforced airframe sees extensive use of titanium alloys, increasing its durability to some 30 years or 6,000 service hours, and raising the maximum takeoff weight to 34.5 tonnes.[38][N 3] Internal fuel capacity was increased by more than 20% to 11.5 tonnes, and could be raised to 14.5 tonnes with the addition of drop tanks; in-flight refueling can also be used to extend missions.[34][37]

Sukhoi has overhauled the avionics suite, at the heart of which is the information management system that greatly enhances man-machine interaction. The system, which has two digital computers, collects and processes data from various tactical and flight-control systems and presents the relevant information to the pilot through the two main multi-function displays, which, together with three secondary MFDs, form the glass cockpit.[39][40] The aircraft features many other upgrades to its avionics and electronic systems, including digital fly-by-wire flight-control system, and the pilot is equipped with a head-up display and night-vision goggles.[41]

The Su-35 employs an Irbis-Epassive electronically scanned array radar that constitutes an essential component of the aircraft's fire-control system. The radar is capable of detecting a 3-square-metre (32 sq ft) aerial target at a distance of 400 km (250 mi), and can track 30 airborne targets and engage eight of them at the same time.[40] The radar can also map the ground using a variety of modes, including the synthetic aperture mode. The Irbis-E is complemented by an OLS-35 optoelectronic targeting system that provides laser ranging, TV, Infra-red search and track (IRST) functionality.[40] The Su-35 is compatible with a multitude of long- and short-range air-to-air missiles, precision and unguided air-to-ground weaponry that include missiles, fuel-air bombs and rockets. A maximum weapon payload of 8 tonnes can be carried on the fourteen hardpoints.[42] Su-35s may use missiles with a range of 200 km[43] and 300 km[44]

The Su-35 is powered by a pair of izdeliye (Product) 117S (AL-41F1S) turbofan engines. Developed jointly by Sukhoi, NPO Saturn and UMPO, the engine is a heavily upgraded AL-31F variant, and draws on the design of the fifth-generation PAK FA's Saturn 117 (AL-41F1) engines. Its thrust output is estimated at 142 kN (31,900 lbf), 20 kN (4,500 lbf) more than the Su-27M's AL-31F.[32] It has a service life of 4,000 hours, compared to the AL-31F's 1,500; the two engines feature thrust-vectoring capability.[38][45] Each thrust vectoring (TVC) nozzle has its rotational axis canted at an angle, similar to the configuration on the Su-30MKI. The thrust vectoring nozzles operate in one plane for pitch, but the canting allows the aircraft to produce both roll and yaw by vectoring each engine nozzle differently. A similar thrust vectoring system is also implemented on the PAK FA.[46]

Design work on the Su-35 had been completed by 2007, paving the way for KnAAPO to construct the first prototype in the summer of 2007. Upon completion, Su-35-1 was ferried to the Gromov Flight Research Institute in Zhukovsky Airfield before being placed on static display at that year's MAKS air show.[49][50] At the time, Sukhoi General DesignerMikhail Pogosyan commented that the aircraft was in great demand abroad, saying Russia was negotiating with several prospective customers and that there were plans to export the aircraft starting in 2010.[51][52]

Preparations began for the aircraft's maiden flight immediately following the air show. Particular efforts were made to debug the flight-control system and test the engine. By mid-February 2008, Su-35-1 had been rolled out to conduct taxiing tests. On 19 February, Sukhoi test pilot Sergey Bogdan took the aircraft aloft for its first flight from Zhukovsky, accompanied by an Su-30MK2 acting as a chase plane.[49][53] During the 55-minute flight, the Su-35 reached a height of 5,000 metres (16,000 ft), and tests were carried out on its stability, controllability and engines. The prototype was put on static display for PresidentVladimir Putin and Prime Minister Dmitry Medvedev the following day.[49]

The second prototype of the modernized Su-35 (Bort 902) at the 2009 MAKS Airshow, where the Russian Defence Ministry placed the launch order for the aircraft

Approximately 40 flights were conducted before the second prototype took to the air on 2 October from KnAAPO's Dzemgi Airport, again piloted by Sergey Bogdan.[54][55] The Su-35 had earlier in July made its first demonstration flight in front of Defence Ministry and foreign officials. At the time, Sukhoi estimated that a total of 160 Su-35s would be supplied to customers worldwide, in particular those in Latin America, Southeast Asia and the Middle East.[56][57] Domestically, the VVS Commander-in-ChiefColonel GeneralAlexander Zelin stated that the service was seeking enough aircraft, estimated to be 24–36 units, to equip "at least two to three regiments".[58]

On 26 April 2009, the fourth Su-35 prototype was destroyed at Dzemgi Airport during a taxi run. The aircraft crashed into a barrier at the end of the runway, burned, and was written off. The pilot, Yevgeny Frolov, ejected and was taken to hospital with burns and other injuries.[59][60] The aircraft was expected to be the third flying prototype, with its first flight scheduled on 24 April, but which was rescheduled for 27 April.[59] A commission was opened to investigate the crash, but several sources initially speculated that the incident had been the result of a brake failure or a faulty fuel pump.[61][62][63]

During the 2009 MAKS air show, the Russian Defence Ministry signed a US$2.5 billion contract for 64 jet fighters, which consisted of a 48-aircraft launch order for the Su-35S ("Serial"). The Russian government promised to provide Sukhoi an additional US$100 million in capital, with additional financial assistance from Sberbank and Vnesheconombank, the latter of which was contracted to provide US$109 million to start the production programme.[8][64][65] The Su-35S's estimated price was $40 million each, and the 64-aircraft contract was the largest aircraft order after the collapse of the Soviet Union.[6] All are expected to be delivered by 2015.[66]

In November 2009, KnAAPO started manufacturing the first serial aircraft; Sukhoi estimated that 24 to 30 aircraft would be produced each year from 2010 to 2020.[67][68] On 11 October 2010, the first production Su-35S had completed general assembly;[69] at this point the preliminary flight test programme had logged 350 flight hours across 270 flights using the two remaining flying prototypes. Sukhoi confirmed that the aircraft had fully met all specifications and parameters, including maximum speed, height, radar detection range and manoeuvrability.[70][71] The first Su-35S took its maiden flight in May 2011.[72]

Following preliminary tests, the Defence Ministry was expected to initiate state joint tests involving six Su-35s to further scrutinize systems such as weapons.[73][74] In early 2012, two aircraft were reportedly planned for delivery in 2011, eight in 2012, twelve in 2013 and 2014, and fourteen in 2015;[75] in 2014, the first delivery was now expected to take place that year.[76]

In March 2015, it was reported that Russia and India signed an agreement to jointly develop a fifth-generation upgrade to the Su-35. A Russian industry source cited in the article that the upgraded Su-35S will cost about US$85 million.[77]

The first prototype Su-35 in August 2011, when state acceptance trials in Akhtubinsk began

Three production Su-27Ms were completed and delivered to VVS in 1996 for testing.[23] They were operated by 929th State Flight Test Center (abbreviated as GLITS in Russian) at Vladimirovka Air Base, Akhtubinsk, performing weapons trials. During one such flights, a weapon pylon, to which a bomb and rocket were attached, fell into a village in Ryazan; nobody was hurt.[78][79] In 2001, the Air Force decided that the aerobaticsteamRussian Knights would receive several Su-27Ms, presumably from GLITS and Sukhoi. After pilots from the team undertook conversion course at Vladimirovka AB, the first of five aircraft was delivered to the team in July 2003. It was expected that the Su-27Ms would enhance the flying repertoire of their new owners, but due to various reasons, they were used as a source of spare parts for other aircraft in the demonstration fleet.[79]

In late May 2011, Sukhoi flew the first Su-35S to the Defence Ministry's 929th State Flight Test Centre at Akhtubinsk prior to states joint tests conducted to prepare the aircraft for operational service with the VVS.[80][81] Official trials commenced in mid-August with the two Su-35 prototypes, before being joined by production aircraft. As of March 2012, four Su-35S units were involved in such tests, operating alongside the two flying prototypes.[80][82] These Su-35s had by April and August 2012, completed 500 and 650 test flights, respectively.[82][83]

The first Su-35S for the Russian Air Force, May 2012

On 28 December 2012, Sukhoi delivered a batch of six serial production Su-35S fighters to the VVS. Defence Ministry officials accepted the aircraft at KnAAPO's manufacturing plant in Komsomolsk-on-Amur, Russia.[84] Five of the six Su-35S delivered in December went to the Gromov Flight Research Institute, where in February 2013 an eighteen-month programme began to test the Su-35's ability to conduct highly maneuverable short-range combat. The programme consists of three components, which are dogfights; the use of weapons and the ability to evade enemy fire; and the ability to destroy helicopters and unmanned aerial vehicles.[85] State-acceptance trials would conclude in 2015, by which time a second 48-aircraft order is expected to have been signed with the VVS.[86] Another 12 Su-35S fighters were delivered in 2013.[87][88]

In December 2012, Russian officials commented that the Swifts and Russian Knights aerobatics teams would receive new aircraft to replace the Mikoyan MiG-29 and Su-27, respectively. The Swifts was expected to receive the Su-30SM and the Russian Knights receive the Su-35. Deputy Prime MinisterDmitry Rogozin commented the upgrade was to "show to the world not only the inimitable skill of our pilots, but also the talent of our aircraft designers who despite all the problems of the past decades, are willing to give us new reasons to be proud of their country.".[89][90] Russian Air Force received another 12 Su-35S multirole fighters on 12 February 2014 to be deployed with an air regiment based in Russia’s Far East. The Defense Ministry ordered 48 of the aircraft in 2009, of which 34 have been delivered so far. The final deliveries of the remaining 14 are due in 2015.[91][92] In December 2013 the Russian Air Force also received 12 Su-35s.[92]

In 2001, Brazil under President Fernando Henrique Cardoso announced the F-X tender to procure a replacement for its aging aircraft including the Dassault Mirage IIID/E and Northrop F-5. Sukhoi partnered with Avibras to submit the Su-27M for the US$700 million tender that would see at least twelve aircraft delivered to the Brazilian Air Force. Other contenders were the Mirage 2000, F-16, MiG-29, and JAS Gripen.[98][99] Any contract would have been accompanied by an offset agreement that would see the winning bidder provide input to Brazil's aviation industry. Had the Su-35 won, Russia would have purchased 50 Embraer airliners for use by Aeroflot.[98][100] The Su-35 and Mirage 2000 were the front-runners to the program, but the former was favoured for its superior flight characteristics. According to the Centre for Analysis of Strategies and Technologies, the Su-35 would have been the first heavy supersonic fighter to be delivered to Latin America.[98][101][102] The tender was suspended for much of 2003 as the newly elected President Luiz Inácio Lula da Silva focused more on social welfare.[103] The tender was again suspended in 2005, pending the availability of new fighters.[104]

In 2007, Russia submitted the modernized Su-35 for Brazil's relaunched F-X2 competition. The tender this time attracted the participation of the Boeing F/A-18E/F Super Hornet, Lockheed Martin F-16BR, Saab JAS Gripen NG, Dassault Rafale, and Eurofighter Typhoon. Brazil was looking to purchase at least 36, and up to 120, aircraft to replace Northrop F-5BRs, Alenia/Embraer A-1Ms, and Dassault Mirage IIIs.[105][106] In October 2008, the Brazilian Air Force selected the Boeing F/A-18E/F Super Hornet, Dassault Rafale, and Saab Gripen NG as the three finalists.[107] In October 2009, Rosoboronexport declared that Russia would provide 120 Su-35s and full technology transfer to Brazil.[108] The Su-35 was expected re-enter the tender after Brazilian President Dilma Rousseff postponed the programme in January 2011 due to fiscal concerns.[105][109][110] In December 2013, the Brazilian government selected the Gripen NG for procurement.[111]

Since the early 1990s, an extensive sales arrangement of the Su-35 to China has been discussed. Sukhoi officials, in 1995, announced their proposal to co-produce the Su-35 with China, contingent on Beijing's agreement to purchase 120 aircraft.[112] However, it was alleged that the Russian Foreign Ministry blocked the sale of the Su-35 and Tupolev Tu-22M bombers over concerns about the arrangements for Chinese production of the Su-27.[113]

In 2006, China was showing interest in the modernized Su-35, and was negotiating with Moscow for a purchase of the fighter.[114][115] At the 2007 MAKS air show, a number of Chinese delegates were seen taking photos and videos of the Su-35 prototypes.[116] In November 2010, Russia, through Rosoboronexport, was ready to resume talks with China on the sale of the Su-35. China reciprocated in 2011 by presenting a proposal on the purchase of the fighter.[117][118]

In March 2012, the Russian media reported that the two countries were in final contract negotiations for 48 Su-35s; the remaining obstacle is reportedly Moscow's demand that Beijing guarantee proper licensing for its Su-35 production.[119][120] China denied this deal because it did not want the Su-35, but only shown slight interest in its 117S engine; at the 2012 Zhuhai Air Show Russia approached China with its 117S engine in a failed attempt to sell Su-35.[121] In late 2012, it was reported that China wanted to purchase only 24 units, which was less than what Russia deemed to be worthwhile, thus stalling negotiations.[122] By late 2012, the negotiations resumed, this time involving 24 aircraft.[123]

In March 2013, media articles stated the two countries signed an initial agreement for 24 Su-35s and four submarines prior to Chinese President Xi Jinping's visit to Russia.[124][125] Russia stated it had not signed an arms agreement with China, which is believed to be interested in the Su-35's NPO Saturn 117S engine.[126] In November 2013, a senior executive with Russia's Rosoboronexport said he expected to finalize the Su-35 order with China in 2014.[127] But according to some reports in early 2014, the fighter sale will not be completed due to undisclosed technical difficulties.[128][verification needed] In November 2014 Sukhoi first deputy director general Boris Bregman said that Russia is ready to supply 'standard' Su-35s to China.[129]

At the 1996 Seoul Air Show, Russia submitted the Su-35 (Su-27M) and Su-37 for South Korea's F-X procurement programme, a 40-aircraft requirement to replace the Republic of Korea Air Force's F-4D/Es, RF-4Cs, and F-5E/Fs. The Su-35 competed against the Dassault Rafale, Eurofighter Typhoon, and F-15K Slam Eagle.[130] The proposed Su-35 featured a phased grid radar and AL-31FP vectoring-thrust engines; final assembly would have taken place in South Korea, the offer included a full technology transfer. The US$5 billion contract may have been partially financed through a debt-reduction deal on money Russia owed to South Korea.[131][132] The Su-35 was reportedly the cheapest aircraft to purchase and maintain, however it was eliminated early in the bidding process, along with the Typhoon. The F-15K, viewed as the competition's front-runner due to South Korea's ties with the United States, was chosen in 2002. Reports have claimed that, had South Korea not chosen the F-15K, the United States would have refused to integrate American weapons on the selected aircraft.[130][133][134]

In 2002, Sukhoi offered Su-30 family aircraft to Australia, including the Su-35.[135][136] However Australia opted for the F-35 to replace the F-111 and F/A-18. Russia has offered the Su-35 to India, Malaysia, Algeria and Greece;[137][138] no firm contracts have materialised, with the first three countries having been occupied with other fighter projects and unlikely to procure the modernized Su-35.[70] In 2010, Libya was expected to sign a contract for twelve Su-35s as part of a bigger military transaction that would have included S-300PMU-2surface-to-air missiles, Kilo-class submarines, and T-90 tanks.[139] The civil war in Libya and the resulting military intervention caused Rosoboronexport to miss out on US$4 billion in arranged contracts as they were never signed.[140][141]

^The NATO reporting name only applies to the first Su-35 (Su-27M), as the that of modernized variant is unknown.

^"T-10" is the in-house designation of the Su-27 family. Derivatives of the type such as the Su-27K and Su-27M have the designations of "T-10K" and "T10-M"; as the modernized Su-35 has a project designation of "T-10BM", it would most likely to have been labelled as the "Su-27BM".[31] However, the media has given it the designation "Su-35BM" to distinguish it from the Su-27M/Su-35, even though neither Sukhoi nor KnAAPO have ever referred to it as such.

^Other sources claim the MTOW is 38.5 tonnes and the empty weight is 16.5 tonnes.[32][34]